KR20070007052A - Improved energy storage method for load hoisting machinery - Google Patents

Abstract

A method for energy storage and recovery for load hoisting equipment powered by an induction hoist motor controlled by a first inverter and having a dual inverter controlling a capacitor utilizing rest power such as reverse power generated from the motor when lowering a load, and unused power at small load or idle, to charge the capacitor whereby energy is stored in the capacitor and the system is reversed when a load is lifted and power is consumed whereby the capacitor is discharged to deliver power to the hoist motor. ® KIPO & WIPO 2007

Description

IMPROVED ENERGY STORAGE METHOD FOR LOAD HOISTING MACHINERY

The present invention is directed to an improvement of the patented energy storage method for using cranes and other load winding devices. In particular, it relates to an improvement in the method for storing energy in a capacitor charged by said load winding device drive motor. When the load is raised and more power is required, this stored energy is resupplied to the system.

The present invention relates to improvements in systems and methods for storing energy in load-wound cranes driven by electrical power. Especially useful in the case of a device driven by a diesel-electric generator that controls a wide range of loads. The system stores energy at reverse power, or small loads, and supplies power at peak power, or large loads. In theory, there has been a mechanical question that only a primary energy source is required to supply a relatively constant average power, and peak power does not need to be supplied. However, to date, the practical aspects of the question have hindered its use.

Combinations of batteries and generator energy storage systems have been used in the past to accomplish the above objectives. In practice, however, battery components present a number of problems. For example, there are small capacities, electrical inefficiencies, physically large battery volumes, heavy weights, and short battery life, so even with state-of-the-art battery techniques, these systems for achieving energy storage are not feasible at present.

A flywheel type energy storage system can also be used to achieve the above-mentioned objectives. However, the flywheel must be able to be driven over a wide range of speeds to store the energy that generates power. In order to transfer energy to the flywheel at various speeds, a DC motor may be best used, but a flywheel driven by a DC motor is not satisfactory for the following various reasons.

1. For the flywheel to store energy, by ½ x I x ω ² , the energy is measured, where I = coefficient of inertia and ω = angular velocity of rotation. Therefore, since the energy is measured by the power of the rotational speed, a higher rotational speed can store more energy in the flywheel. However, due to the weak centrifugal force of the coil components of the rotor, the DC motors interconnected to the flywheel have strict rotational speed limits.

2. The DC motors require constant maintenance such as brush replacement, rectifier repair, and insulation.

3. DC motors are relatively large, heavy and expensive.

For these and other reasons, the energy storage type system driven by the flywheel, using a DC motor, is not practical for this purpose.

In recent years, the development of inverter technology has progressed until AC squirrel cage induction motors using inverters have replaced DC motors. The inverter can use a random frequency to convert DC to AC and also reverse-convert AC to DC. By virtue of the AC irregular frequency, the AC squirrel cage induction motor can rotate with an irregular rotational speed that increases up to very high speeds that solve some of the problems described in connection with DC motors.

1 illustrates a general example of a diesel-generator power source currently used and a mechanical device driven by an induction motor for a load winding mechanism controlled by an inverter. The diesel engine 11 is mechanically interconnected to the AC generator 13. The alternating current output from the generator is converted by the diode 15 to direct current. Using an irregular frequency by the inverter 17, DC is converted to AC. The squirrel cage induction motor 19 is driven by AC, which in turn drives the drum 21 which raises and lowers the load. Increasing and decreasing the speed are controlled as a result of the alternating frequency generated and controlled by the inverter. When the load is lowered, reverse AC current is generated by the induction motor. The reverse current is consumed by the resistor 25, allowing the induction motor to perform degenerative braking effectively.

FIG. 2 illustrates a general example of the current entering the system from the utility power grid 27 by a cable power supply 29 that replaces the diesel engine / generator combination of FIG. 1. The incoming voltage is lowered by the transformer 31. Then, by the DC converter 16, an alternating current is converted into DC, from which the system becomes like the system shown in FIG.

While the load 23 is lowered, a reverse-current is sent back to the power grid 27, which in this embodiment is used by other consumers. However, because the reverse-power current includes surge and deviation frequency, other consumers are reluctant to receive it. In the future, it is expected to prohibit reverse power from being sent back to the power grid. In this case, as in the system of FIG. 1, the reverse-power will be consumed by the resistor.

3 illustrates an improvement of the prior art that is inserted into the system by replacing the resistor of FIG. It was issued on August 10, 1999 in U.S. Patent No. 5,936,375, entitled "Methode for Energy Storage for Load Hoisting Machinery." The present invention further includes improvements that are not clearly defined in the design.

The method of the present invention is provided for energy storage and recovery for a load transfer mechanism system powered by an induction motor controlled by a first inverter. The method then drives the induction motor to function as a generator to produce reverse power when the load is lowered or stopped, wherein the load winding mechanism is in a small load state or an idle state. When the reverse power is combined with the unused power, the combined power is formed as rest power, using the rest power to charge a capacitor, and the rest as a dual inverter. Controlling the power; and discharging the capacitor to supply power to the induction motor when the induction motor consumes more than its average power consumption.

Further, the present invention provides a logic controller for measuring energy stored in the capacitor, measuring voltage at the power input side of the first inverter, and programming the energy value of the stored energy and the measured voltage. And transmitting to a programmable logic controller (PLC) and comparing the measured voltage with a specified value in the controller to determine whether the capacitor should be charged or discharged.

 When the controller determines whether the voltage measured at the power input side of the first inverter is higher than the specified value, the dual inverter converts the output of the first inverter to charge the capacitor,

When the voltage is lower than the predetermined value, the dual inverter converts and controls the output of the capacitor delivered to the first inverter, thereby supplying power from the capacitor to the induction motor. An energy storage system of a load transfer mechanism comprising an induction motor controlled by a first inverter, interconnected to a wire rope drum for raising and lowering a load, the system comprising: a capacitor for storing and discharging energy; Sensing the voltage at the power input side of the first inverter and the capacitor controlled by the dual inverter, a programmable logic controller (PLC) controlling the dual inverter, and sensing the voltage at the capacitor Means for generating a power for the load transfer mechanism and programmed logic for the programmable logic controller (PLC) to compare the sensed voltage with a specified voltage value. AC generator (ACG) driven by the AC output of the ACG It characterized in that it comprises a diode configured to control.

In energy storage for winding machinery driven by induction motors, it is an important object of the present invention to provide an improved method for reducing the overall power requirement for the machinery to operate.

It is a further object of the present invention to provide an improved method in which a winding machine driven by an induction motor averages the power consumption requirements of the machine in energy storage for operation.

Another object of the present invention is a winding machine driven by an induction motor, which eliminates the need to transfer power back to the source when the motor is driven by lowering the load, or eliminating the need to absorb power from a resistor or brake. It is to provide a method for the operation of the device.

It is a further object of the present invention to provide an energy storage method that can use a flywheel for electrical energy storage in order for the winding mechanical device driven by an induction motor to operate.

It is a further object of the present invention to provide an apparatus for an energy storage system using a capacitor to store energy of a winding mechanical device driven by an induction motor.

1 illustrates a conventional drive mechanism arrangement for an autonomous load-winding crane.

2 illustrates another arrangement of a conventional drive mechanism for a crane driven by electric power.

3 illustrates a conventional patented method for energy storage for a load winding machine.

4 illustrates a modification of FIG. 3 with the capacitor / condenser energy storage system of the present invention added.

5 is a graph illustrating the relationship between the frequency alpha and the voltage at point A in FIGS. 3 to 4 in which the second inverter controls the AC frequency.

6 is a diagram illustrating a basic relationship of the graph of FIG. 5.

FIG. 7 illustrates a more realistic relationship of a graph suitable for changing the complex load of the operation of the crane of FIG. 5.

8 illustrates a basic power consumption graph in an arrangement of standard prior art load transfer machinery.

Figure 9 illustrates an ideal power consumption graph for a drive mechanism arrangement using the method of the present invention.

FIG. 10 is a power consumption graph of FIG. 10 showing idle power being formed and power being stored.

1-3 illustrate the prior art as described above in the Background section of this specification. FIG. 3 illustrates a patented device that modifies the device of FIG. 1 by adding a portion depicted inside the dashed line. The description of FIG. 1 in the background section relates to the operation of the main device items 11, 13, 15, 17, 19, 21, 23.

Reference is made to FIG. 3 to illustrate the background of the invention. When the load 23 is raised by the winding machine 21, in both the prior art and in the case of the present invention, electrical energy from the local facility power grid, or from an autonomous diesel engine powered by the generator 13. Electrical energy can be used to operate the first induction motor 19, which is connected to the load winding wire rope drum 21 by mechanical power transfer means. By the induction motor, power is consumed while winding the load, and the power is generated while unloading the load.

The energy storage system patented in FIG. 3 is shown surrounded by dashed lines, which consists of an additional mechanical device that replaces the resistor 25 of FIG. 1. The energy storage system includes a second inverter 35, a second induction motor 37, a tachometer or pulse generator 39 for detecting rotational speed, a flywheel 41, and a programmable logic controller (PLC). logic controller 43).

When the load is lowered by the winding mechanisms 19, 21, energy is stored in the rotation of the flywheel 41. This occurs according to the following procedure. The first winding motor 19 of the system reverses while the load winding drum 21 lowers its winding motor, ie the load 23. The first induction motor functions as a generator for generating AC current, or reverse power. By the first inverter 17, the generated AC current is converted into DC, and the DC current flows between the diode 15 and the first inverter 17. As a result, the voltage at point A becomes high.

The voltage at the point A is also high when the load winding mechanism is idle, stationary, or when winding a light load. When the power consumption of the load winding mechanism is very small or nearly zero, the electricity supplied via the diode 15 from the main power source, or the AC generator, or the local facility power grid raises the voltage at point A. This produces unused power. When the load winding mechanism winds up heavy loads, and when its power consumption is large, the voltage at the point A becomes lower due to the lack of electricity.

In the case of being driven to function as a generator when unloading, the energy storage system is operated such that both this unused power and the generated reverse power controlled by the first induction motor 19 are stored. The combination of unused power and reverse power is formed as a rest power.

The idle power is controlled by the second inverter 35. The second induction motor 37 may be driven by the idle power and controlled by the second inverter to rotate the flywheel 41. When the voltage at point A is high, the idle power is stored in the rotational energy of the flywheel. The system operates to recover power from the rotational energy of the flywheel and to supply electricity shortages when the voltage at the point A is low.

The voltage measured at point A and the rotational speed detected by the tachometer or pulse generator 39 connected to the flywheel 41 are transmitted or input to the PLC 43. The PLC controls the second inverter 35 using the control frequency to change DC to AC. Depending on the voltage at point A and the rotational speed of the flywheel, the frequency is controlled by the programmed logic of the PLC. The voltage at point A is manually compared with the set voltage value V ₀ specified in the programmed logic.

Reference is again made to FIG. 3. Expensive and complicated device parts of the patented prior invention, namely the second induction motor 37, the flywheel 41 and the pulse generator 39, disappear according to the invention. With reference to FIG. 4, additional and alternative devices of the invention are inserted in the prior art and current implementations depicted in FIGS. 1-3. The patented conventional device of FIG. 3 shows that it is modified by the inventive technique of FIG. The capacitor, or the capacitor 45, replaces the three conventional items 37, 39, 41, and the dual inverter 35 is replaced in place of the second inverter 35 of FIG. 3 in FIG. 4. This greatly simplifies the device configuration and generally reduces the overall cost.

4 illustrates an embodiment of the device of the present invention, wherein when the voltage at point A is higher than the set (or specified) value V ₀ , the PLC 43 sends a first to the dual inverter 35. The inverter is commanded to convert the output to DC, whereby the capacitor 45 is charged and power is stored as latent energy. If the voltage at point A is lower than the set value V ₀ , the dual inverter controls the capacitor and is thereby discharged, thereby generating power to be supplied to the induction motor 19, whereby energy is recovered from the capacitor.

The dual inverter 35 of FIG. 4 controlling the capacitor 45 is in turn controlled by the PLC 43 so that the DC output of the capacitor 45 can be efficiently delivered to the first inverter 17. Similarly, DC for conversion by the first inverter controls AC to drive the induction motor 19, and vice versa.

For the relation between the voltage at point A and the AC frequency alpha α, see FIGS. 5 to 7 (see also FIGS. 3 and 4). The frequency of alpha is determined by the voltage at A. When the load of the load on the winding drum is small and there is no large power consumption, or when reverse power is generated by the lowered load, the voltage at A becomes greater than the set value V _{0 of the} controller close to the average voltage. In this case, the frequency alpha is a positive number and energy is stored in the capacitor. When the load of the load is large and power is consumed, the voltage at A becomes lower than the set value V ₀ , the frequency alpha becomes a negative number, and energy is recovered from the flywheel rotation.

When the voltage at A is equal to the set value V ₀ , energy is neither stored nor recovered by the energy storage system. The set value V ₀ is determined by the average load and the mechanical and electrical efficacy. The reduced capacity requirements for the diesel engine and AC generator for the operation of the load winding mechanism allowed by the present invention are determined from the average load and the mechanical and electrical efficacy.

Referring to Fig. 8, a graphic power consumption table that can be applied to the present invention is shown. It can be used for load moving mechanisms such as winding machines, cranes, tractors, trains where the load to be moved varies greatly or the change in inertia due to the acceleration and deceleration of the load occurs greatly. In the case of a winding machine or crane, the variable weight load is raised and lowered, in which case the load is accelerated and decelerated. In FIG. 8, the power consumption of the induction motor is graphically depicted for operation with a particular load. At this time, block A represents the power consumption required to accelerate the load to speed up, and block B represents the power consumption required to move and lift the load at a constant speed. Block C represents the power dissipation needed to slow the load down, block D represents the reverse power, or braking effect, required for the load to descend at a constant speed, and block F represents the load descending. Shows the reverse power / breaking effect needed to slow down. When the load is wound, the system consumes power. When the load is lowered, the motor operates to produce power and functions as a brake.

Referring to FIG. 9, a graphical representation of power consumption, which can be achieved using the present invention, is shown. The power input is constant and there is unused power when the machine does not lift the load, for example when it is idle or not at shutdown. The hatched area of FIG. 9 superimposed on the power consumption graph of FIG. 8 represents the average power consumption.

10 shows a graphical table of rest powers stored in the system of the present invention. When the energy storage system of the present invention is used, idle power, including power not used at reverse power and small load, or in an idle state, is stored as the rotational energy of the flywheel, the stored energy being the peak load, Or in case of large loads. The reverse hatched area in FIG. 10 represents the idle power. As shown in Fig. 9, the capacitor of the main power source is sufficient to supply the average power consumption. When the load is lowered by winding, the average power consumption is equal to the mechanical and electrical efficiency losses.

The present invention includes a method for energy storage and recovery for a load transfer mechanism powered by an induction motor controlled by a first inverter. The steps of the method include driving the induction motor to function as a generator when the load is unloaded or stopped to produce reverse-power. The reverse power combined with unused power is formed as idle power when the load winding mechanism is in a small load or idle state. The idle power is used to charge the capacitor controlled by the dual inverter. When the induction motor consumes more than average power consumption, the capacitor is discharged to power the motor.

The method also includes measuring the energy (voltage) stored in the capacitor and measuring the voltage at the power input side of the first inverter controlling the induction motor. Capacitor energy measurements and the voltage measured at the inverter input are sent to a programmable logic controller (PLC). The measured voltages are compared at the controller using a specified value that determines whether the capacitor should be charged or discharged to be driven or driven by an induction motor. In the method, when the controller determines that the voltage measured at the power input side of the first inverter is higher than the set value, the dual inverter converts the output of the first inverter to charge the capacitor, thus energy Is stored in the capacitor. Thus, when the voltage is lower than the set value, the dual inverter converts and controls the output of the capacitor delivered to the first inverter, thereby supplying power recovered from the capacitor to the induction motor.

Thus, the energy storage system of the present invention is very efficient so as to reduce the capacity of diesel engines and AC generators, and the amount provided from the power source, thus providing a less expensive load winding device according to the present invention. In addition to providing, efficient energy can be provided. Also, in the case where the power source is not stable and the fluctuations are severe, the energy storage system of the present invention can be used as a power stabilizer.

The invention also includes a novel apparatus for carrying out the method of the invention. The energy storage system of the load transfer mechanism includes an induction motor connected to a wire rope drum for raising and lowering loads. The motor is controlled by a first inverter. The energy storage system includes (a) a capacitor for storing and discharging energy controlled by a dual inverter, (b) a programmable logic controller (PLC) for controlling the dual inverter, and (c) a first inverter. Means for sensing a voltage at the power input and sensing the voltage of the capacitor; (d) logic programmed for the PLC for comparing the sensed voltage and the output of the pulse generator with a set voltage value. The energy storage system also includes an engine driven by an AC generator (ACG) that generates power for the load transfer mechanism, and a diode that controls the AC output of the ACG.

Claims (4)

An energy storage and recovery method for a load winding machine device powered by an induction motor controlled by a first inverter, the method comprising: When the load is lowered or stopped, the induction motor functions as a generator to drive to produce reverse power, when the load winding mechanism is in a small load state or idle state; Reverse power is combined with unused power, the combined power being formed as a rest power; Using the idle power to charge a capacitor, Controlling the idle power with a dual inverter, and Discharging the capacitor to supply power to the induction motor when the induction motor consumes more than its average power consumption Energy storage and recovery method for a load winding machine comprising a. The method of claim 1, Measuring energy stored in the capacitor, Measuring a voltage at a power input side of the first inverter, Transmitting the energy value and the measured voltage of the stored energy to a programmable logic controller (PLC), and Comparing the measured voltage with a specified value at the controller to determine whether the capacitor should be charged or discharged Energy storage and recovery method for a load winding machine comprising a. 3. The dual inverter of claim 2, wherein when the controller determines that the voltage measured at the power input side of the first inverter is higher than the predetermined value, the dual inverter converts the output of the first inverter to charge the capacitor. , When the voltage is lower than the specified value, the dual inverter converts and controls the output of the capacitor delivered to the first inverter, thereby supplying power from the capacitor to the induction motor. Energy storage and recovery method for the device. An energy storage system of a load transfer mechanism comprising an induction motor controlled by a first inverter, interconnected to a wire rope drum for raising and lowering loads, the system comprising: A capacitor for storing and discharging energy, the capacitor controlled by a dual inverter, A programmable logic controller (PLC) for controlling the dual inverter, Means for sensing a voltage at a power input side of the first inverter and sensing a voltage at the capacitor, Programmed logic for the programmable logic controller (PLC) to compare the sensed voltage with a specified voltage value, An AC generator (ACG) driven by an engine that produces power for the load transfer mechanism, Diode controlling the AC output of the ACG Energy storage system of a load transfer mechanism comprising a.

Images